Bluetooth is a wireless communication protocol for exchanging data between devices. A variety of devices communicate using the Bluetooth protocol including mobile phones, headsets, tablets, computer mice, keyboards, printers, PC networks, media players, video game consoles, GPS receivers, and physical activity trackers.
Bluetooth is a packet-based protocol. For each pair of communicating devices, one device acts as a master and the other device acts as a slave. Packet exchange is timed according to the master's clock which marks 625 μs time slots. Data packets may be one, three, or five slots long. For single-slot packets, the master transmits in even slots and receives in odd slots; the slave, conversely, receives in even slots and transmits in odd slots. Irrespective of packet length, the master begins transmitting in even slots and the slave begins transmitting in odd slots.
Bluetooth devices operate on 40 separate channels in the radio frequency range of 2400-2480 MHz. Each channel has a bandwidth of 1 MHz with 2 MHz between adjacent channels. A pair of connected devices changes channels every 625 μs (called “frequency hopping”). When two pairs of devices happen to select the same channel at the same time, their signals interfere and corrupt each other. When two transmissions interfere, the connected devices may initiate an error correction or retransmit the corrupted portion of data.
The background of the invention is neither exclusive nor exhaustive and is intended neither to describe all uses of the invention nor to limit the scope of the invention.